Variable inductor conversion system



May 6,1969 L. K. WANLASS VARIABLE INDUCTOR CONVERSION SYSTEM Original Filed May 14, 1965 Sheet Ea i4 M/EA/T 2 4654/5 56/57 Mam/Z155 By a I May 6, 1969 1.. K. WANLASS I VARIABLE INDUCTOR CONVERSION SYSTEM Original Filed May 14, 1965 Sheet ATTOE/VEVfi- May 6, 1969 L. K. WAN LASS VARIABLE INDUCTOR CONVERSION SYSTEM Original Filed. May 14, 1965 Sheet Ira 54 MWE/VTOE 4654/5 (9V7 mwmss. 5y

Arrae/veya May 6, 1969 K. WANLASS 3,

VARIABLE INDucToR CONVERSION SYSTEM Original Fild May 14, 1965 Sheet 5 of e H61 J5, AMPd/F/[3 w L. K. WANLASS 3,443,198

VARIABLE INDUCTOR CONVERSION SYSTEM Sheet 6 of 6 May 6, 1969 Original Filed May 14, 1965 yfi ga A TTOE/VE V5 United States Patent O Int. Cl. H02m 7/68, /16

US. Cl. 32125 27 Claims ABSTRACT OF THE DISCLOSURE Conversion systems in which conversion of AC to DC, DC to AC, or frequency conversion is accomplished by use of an inductor, the impedance of which can be electrically varied. The inductor comprises a first winding wound on a magnetic core having four legs or common regions joined by end regions. A source of control current, either AC or DC, is connected to another winding wound on the core generally transverse to the first winding, the control current in the second winding controlling the inductance of the first. For AC to DC conversion, the AC is applied to the first winding and a unidirectional current applied to the other winding; for DC to AC, the reverse is true. For frequency quadrupling, a pair of the variable inductors are cascaded.

Cross-references to related applications This is a division of my copending application Ser. No. 455,939, filed May 14, 1965, now Patent No. 3,403,323, for Electrical Energy Translating Devices and Regulators Using the Same, which is a continuation-in-part of my application Ser. No. 857,083, filed Dec. 3, 1959, for Ferromagnetic Signal Transfer Device, now abandoned, the disclosures of which are incorporated by reference herein.

The properties of ferromagnetic materials have long been utilized in the design and construction of components for electrical circuitry. Signal translating devices which make use of the property of magnetization range from a simple inductor comprising a coil wrapped around a ferromagnetic core to complicated magnetic amplifiers and saturable transformers. Such devices are particularly useful because they permit the easy control of their primary electrical characteristics. This control, moreover, is itself electrical and thus permits a wide selection of control functions. For example, if it is desired to control the average impedance in a line, a saturable reactor can be utilized and the average impedance of the reactor to the line signal varied as a function of a DC control current applied to the control winding of the reactor. The principle of operation of such saturable reactors is well known and they are widely used. On the other hand, if it is desired to electrically control the coupling between primary and secondary windings of a transformer, they can be wound around a core and the flux linkage controlled by the current applied to a control winding. Ordinarily, this control is exercised by varying the flux density of a shunt leg of the core positioned between the primary and secondary legs to cause differing amounts of flux from the primary to traverse the shunt leg.

In both the saturable reactor and the saturable transformer discussed above, control depends upon the core being driven into saturation. This switching type operation results in distortion which in many cases is unacceptable. In order to increase the power capacity of such devices, the art has turned to larger and larger volume cores so that the range of signals that can be handled is increased. Regardless of the size of the cores, however, such devices cannot provide control over a large range and invariably introduce unacceptable distortion into the line signal. Moreover, precautions must be taken to insure that the AC signal, in the load winding, in the case of a saturable reactor, and the primary winding in the case of a saturable transformer, does not induce a large signal in the DC control winding. This is generally prevented by providing a pair of AC windings which are so related to the DC winding that the AC fluxes generated by them are cancelled out. While this is satisfactory, it further adds to the size, cost and complexity of the device.

According to the present invention, signal translating devices are provided which overcome the major disadvantages of previously known magnetic core devices. The devices of the present invention are arranged such that operation takes place without the requirement of saturating the magnetic circuit and consequently distortion can be greatly reduced in the signal translation. In addition, the range of control of the present devices is very much greater than those devices presently known. The present devices may be made much smaller in size, less complex, and consequently less expensive than presently obtainable devices. All of these desirable features result from the provision of devices having cores in at least one portion of which a control current generated flux component and an AC generated flux component are in opposition at all times, i.e., on both halves of the AC cycle. As a result, the complete path of the AC flux within the core is not saturated and the composite B-H characteristic of the core can be maintained within its nonsaturated region. Since these two flux components always are in opposition in at least one portion of the path of the AC generated flux component, an increase in control current which may, for example, be DC means that an increase in AC current can be tolerated without distortion. This is, of course, opposite to the situation present in the present day devices where a larger DC current means that the AC signal must be correspondingly reduced.

Because the sense of the AC generated flux component reverses every half cycle, and the sense of a DC generated flux component remains constant, in order to have a core having at least one portion in which at all times the DC flux component and the AC flux component are in opposition, it is necessary to provide the core with four regions in which both the AC and the DC flux components appear and two end or joining portions for magnetically coupling the common regions. For the sake of convenience, the common regions will hereafter be referred to as legs although it should be understood that it is not necessary to have a structure in which actual structurally identifiable legs are present. By properly positioning a pair of coils on such a core, a DC flux component can be caused to follow paths through legs 1 and 2 and through legs 3 and 4 and an AC flux component caused to follow paths through legs 1 and 4 and through legs 2 and 3. The AC flux component, of course, reverses its direction each half cycle. These relationships will be described in greater detail in connection with the drawings.

On each half cycle, however, AC and DC flux components will exist in each leg and will be in opposition in a first pair of diagonal legs and in addition in the other pair of diagonal legs. For example, for a first sense of the AC flux component, legs 1 and 3 may have the AC and DC flux components in opposition while legs 2 and 4 will have these flux components in additive relationship. It can thus be seen that each of the two legs in each of the paths of the AC flux will be at different points on the magnetization curve of the core material. The leg in which the flux components are additive (the additive leg) will be relatively far out on the magnetization curve and consequently will have a lower permeability and a higher reluctance while the leg in which the flux components are in opposition (the bucking or opposing leg) will have a higher permeability and a lower reluctance. As used in this specification, the terms higher and increased and lower and decreased as applied to permeability and reluctance are, of course, meant to be relative to the permeability and reluctance of the core when only the larger flux is present, or to state it another way, lower or reduced reluctance means the reluctance is closer to the nominal reluctance of the core material and higher or increased reluctance means the reluctance is further from the nominal reluctance.

Since the total magnetic circuit encompossed by the load winding will include an additive leg and a bucking leg, the composite B-H characteristic of the circuit will be a composite of the two and will have a lower average permeability than would the same path Without the presence of the DC flux component. The average permeability of the path will decrease as the DC flux component is increased and consequently the composite B-H curve will be caused to rotate in a clockwise direction. Such a rotation indicates a decrease in average permeability and a corresponding decrease in average inductance presented to the AC or load winding, and consequently it can be seen that by increasing the DC flux component, the inductance presented to the load winding is decreased. The device of the present invention can thus be likened to a conventional ferromagnetic core having a variable air gap therein.

When constructing a variable inductance device in accordance with the present invention, the AC winding and the DC winding are preferably positioned on the core so that there is little or no voltage induced in the DC winding over the preferred operating range. This is conveniently done by positioning the windings at right angles, that is, with their axes transverse. As pointed out above, in one portion of its path, the AC generated flux is called upon to travel from a leg, for example, leg 4, of high permeability to a leg, leg 1, of low permeability. The flux passing through leg 4 could, however, also complete a path by diagonally crossing the end portion and travelling through high permeability leg 2. instead of low permeability leg I. Since reluctance to magnetic flux can be approximately expressed as:

R=l/,uA where:

R'=reluctance l=length of path ,u.=permeability A=area of the path it can be seen that if the DC fiux component is made high enough, a point will be reached as the AC flux component increases where the permeability in leg 2 will be sufficiently lower than the permeability in leg 1 that the differences in the length of the path between leg 4 and leg 1 and leg 4 and leg 2 will be overcome and some of the flux from leg 4 will complete its path through leg 2.

As a result of this crossover flux, an AC voltage will be induced in the DC winding. For low values of DC or AC current, however, the effect of this crossover flux will be negligible and will not effect the inductance of the AC winding. The DC winding can be provided with a suitable choke to suppress the AC voltage induced therein as a result of the crossover flux.

According to the present invention a variable transformer can be provided by winding a further winding on the core with its axis parallel to that of the DC winding, this third winding being secondary of the transformer and the aforementioned AC winding being the primary. In the absence of any DC control current there is substantially no coupling between the primary and the secondary .4 windings because they are wound about transverse axes. As the DC control current is increased, there is an increased transfer of power from the primary to the secondary winding. The operation of such a variable transformer can best be explained in the following manner.

Consider that the primary current sets the level of the inductance of the secondary Winding. As the primary current increases, the inductance of the secondary winding decreases and the voltage induced therein increases since:

If the frequency of the control voltage is much less than the frequency of the primary,

becomes inconsequential. Therefore:

It can thus be seen that the voltage induced in the secondary is dependent on the change of inductance which is caused by the fluctuation of the primary current. As the primary current increases, L (of the secondary) decreases and the voltage induced in the secondary increases.

The phenomenon of crossover flux also contributes to the development of a voltage in the secondary winding of the transformer, As the secondary winding is wound with its axis parallel to that of the DC winding, the crossover flux will cut the turns of the secondary winding and induce a voltage therein, As the DC control current becomes greater, the permeability in the various legs will change as will the reluctance of the various paths so that more and more crossover flux is produced as the AC current increases and more and more voltage is consequently induced in the secondary windings. For very high DC and AC flux component values, a significant part of the AC flux can be caused to cross over with a resulting voltage being induced in the secondary winding. It appears, however, that at normal operating levels, the greater portion of the power transfer occurs as a result of the inductance phenomenon explained above.

The theories expressed above are believed to describe the physical phenomenon present in the system and are believed to be more accurate than those expressed in my above-mentioned original application. However, it should be'understood that the principles governing the operation of the devices of the present invention have not been completely developed and it is possible that further theoretical bases for operation will be discovered. The theories discussed in this application, and in my original applica tion, should therefore be taken only as the best presently available and are not meant in any way to limit the scope of the present invention.

While the foregoing theoretical description has discussed the devices of the present invention as variable inductors and variable transformers, the devices, by their nature, may be used in many different kinds of circuits, even in circuits where a conventional variable inductor or variable transformer would or could not be used. For example, the variable inductor has been described primarily with regard to a device wherein the impedance presented to an AC load winding is varied by varying the direct current in a control winding. Such a device has obvious utility in regulators and the like. However, there are additional ways in which the variable inductor could be used. Thus, in addition to the situation where the load signal is AC and the control signal is DC, the

load signal could be DC and the control signal AC or both the load signal and the control signal could be AC as will be more fully described.

The variable transformer of the present invention may be operated in either of two modes; a frequency doubling mode and a non-frequency doubling mode. In the first of these modes, the frequency of alternating current signals are doubled in transfer from the primary to the secondary circuit.

The frequency doubling phenomena can also best be explained in terms of inductance. As pointed out above, the primary current sets the level of the inductance of the secondary winding. Inductance is, of course, an absolute quantity and thus the inductance of the secondary winding changes twice for each cycle of primary current and hence the output has a double frequency.

The crossover flux phenomenon also provides a partial explanation for the frequency doubling phenomena. At proper input levels, when an alternating current'signal is applied to the primary winding, a voltage will be induced in the secondary winding at twice the input frequency. This occurs because in each half cycle of the alternating current input, the diagonal path followed by the crossover flux switches; for example, on the first half cycle the flux will cross over from leg 1 to leg 3 while on the second half cycle the flux will switch and cross over from leg 2 to leg 4. However, each of these diagonal paths cuts the secondary winding in the same direction and consequently the voltage induced in the secondary will be in the same direction regardless of the diagonal followed by the crossover flux. The secondary Winding thus in effect sees the modified absolute value of the input such as is done by a full wave rectifier. When a modified absolute value is taken of a sine wave, the result is an output waveform with twice the frequency of the input.

Since the alternating flux component in the legs is essential to set up the proper reluctance pattern, the crossover flux is not immediately responsive to the input but rather builds up slowly, as the slope of the output waveform is zero at the time the slope of the input waveform is maximum, that is, when it crosses zero. The same phenomenon also acts at the end of each half cycle of the input with the result that the output waveform is rounded out and has a frequency twice that of the input, although somewhat distorted.

The variable transformer of the present invention can also be operated in a non-frequency doubling mode by establishing a bias flux in the paths followed by the alternating flux of a magnitude suflicient to insure that the direction of the composite bias and alternating flux does not reverse, that is, by setting the magnitude of the bias flux at least as high as the maximum alternating flux.

The nondoubling mode is also explained in accordance with the inductance theory. If the primary flux never crosses zero, there is only one point in each cycle of the input where the inductance of the secondary is a maximumthe peak of the positive going half cycle. Similarly there is only one point of maximum inductancethe peak of the negative half cycle, Since the control current never changes sign, there is no absolute value taken and consequently the output has the same frequency as the input.

From the standpoint of the crossover flux phenomena, it can be seen that with the high bias flux, the same pair of diagonal legs will always have the lower reluctance and the crossover flux will always follow the same diagonal path. The waveform of the crossover flux will not follow the input current waveform because the lower reluctance of the legs is already established by the primary bias and hence as soon as the alternating flux begins to increase, it will begin to cross over. The crossover flux will rise to a maximum when the alternating current input is at a maximum anrl follows its decline.

When the alternating current passes its zero level, however, the crossover flux will still be in the same diagonal and in the same direction and the output will continue to decrease until the input again begins to increase. This is unlike the nonbiased case where the diagonal switched when the input crossed zero and the crossover flux again began to increase.

Another system in which the transformer of the present invention is particularly useful is that of a DC power regulator. In conventional DC power supplies, a low voltage AC power source is normally raised to a desired voltage level in a power transformer, changed to pulsating DC in a rectifier circuit, and filtered to approximate DC in a filter circuit. The output amplitude of the power supply is customarily controlled by variable impedances in series with the flow of energy through the circuit. According to the present invention, the power transformer is replaced by a frequency doubling transformer as described above, which provides two very important im provements: (l) a 50% reduction of ripple in the output voltage with the same filter circuit, or a 50% reduction in filter size with no increase in output ripple; (2) a built-in output voltage control which is not in series with the flow of energy, and which can be varied without atfecting circuit losses, and which can be remotely controlled in an extremely simple manner.

In regulated power supplies, this invention provides the additional advantages of a built-in regulation circuit. In prior art regulated power supplies, a feedback signal was employed to vary the impedance of a variable element, such as a vacuum tube, transistor, or saturable reactor, which was connected in series with the energy flow through the circuit. In this method, the variable element was necessarily large to accommodate the energy fiow, and energy was necessarily wasted therein. The regulated power supply of the present invention overcomes these difficulties by utilizing the control winding of the variable transformer as the variable control element, thereby eliminating the separate variable element formerly employed. Furthermore, the output is controlled at a low energy point in parallel with the energy flow through the circuit, rather than in series, with the result that losses are reduced. If desired, of course, the nondoubling mode of operation could also be employed in such a circuit.

It is an object of the present invention to provide a magnetic electrical energy translating device in which the magnitude of the energy being translated can be electrically varied.

It is another object of the present invention to provide such a device which is smaller than those presently available but which nevertheless has a greater energy translating capacity.

It is also an object of the present invention to provide such device which has a greater range through which control can be exercised without unduly distorting the waveform of the input thereto.

It is a further object of the present invention to provide an improved variable inductance device.

It is a still further object of the present invention to provide such a variable inductance device in which the inductance can be varied electrically.

It is yet a further object of the present invention to provide a ferromagnetic variable inductance device the inductance device the inductance of which can be varied without saturating the device.

It is a still further object of the present invention to provide a rectifying system incorporating such an improved variable inductance device.

It is yet another object of the present invention to provide a DC to AC conversion system incorporating such an improved variable inductance device.

It is also an object of the present invention to provide an amplifier incorporating such an improved variable inductance device.

It is also an object of the present invention to provide a ferromagnetic control device having a load winding and a control windin g in which there is negligible coupling between the windings over the normal operating range.

It is another object of the present invention to provide an improved variable transformer.

It is also an object of the present invention to provide such a variable transformer in which the degree of coupling can be varied electrically.

It is a further object of the present invention to provide a ferromagnetic variable transformer device the degree of coupling of which can be varied without saturating the device.

It is still another object of the present invention to provide a frequency qu-adrupling system incorporating such an improved variable transformer.

Other objects and advantages of the present invention will become more apparent upon reference to the accompanying description and drawings in which:

FIGURES 1, 2, 3 and 4 show a first embodiment of the present invention and illustrates the principles of operation thereof;

FIGURES 1A, 2A, 3A and 4A are views taken along lines 1A-1A; 2A2A; 3A3A and 4A4A of FIG- URES 1 through 4 respectively, with the winding removed for the sake of clarity;

FIGURE 5A illustrates the magnetization curve of a flux path in the core shown in FIGURES 1 through 4 when only a single flux generating means is present;

FIGURES 5B and 5C show the magnetization curves of the individual legs of the core shown in FIGURES 1 through 4 through which pass two fluxes in opposing relationship during one-half cycle and an additive relationship during the other half cycle of an AC current;

FIGURE 5D shows the composite magnetization curve of the core shown in FIGURES 1 through 4 which includes one leg in which two independently generated fluxes are in opposing relationship and one leg in which the fluxes are in additive during one-half cycle and vice versa during the other half cycle of the AC current;

FIGURE 6 shows the relationship between control current and inductance in a device constructed according to the present invention;

FIGURE 7 shows a second embodiment of the present invention;

FIGURE 8 shows a third embodiment of the present invention;

FIGURE 9 shows a fourth embodiment of the present invention;

FIGURE 10 is a schematic diagram of a half-wave rectifier utilizing a variable inductor according to the present invention;

FIGURE 11 is a schematic diagram of a half-wave rectifier utilizing the variable inductor of the present invention in combination with a transformer;

FIGURE 12 is a schematic diagram of a full-wave rectifier utilizing a pair of variable inductors according to the present invention;

FIGURE 13 is a schematic diagram of a DC to AC converter utilizing a variable inductor of the present invention;

FIGURE 14 is a schematic diagram of an amplifier utilizing the variable inductor of the present invention;

FIGURE 15 is a schematic diagram showing two frequency doubling circuits according to the present invention connected in cascade to form a frequency quadrupling circuit;

FIGURE 16 is a schematic diagram of a power supply utilizing the variable transformer of the present invention; and

FIGURES 17A, 17B, and 170 are schematic representations of cores constructed according to the present invention in which the windings are not arranged at right angles.

The principles of operation of the present invention as discussed above may further be explained by reference to FIGURES 1, 1A, 2, 2A, 3, 3A, 4 and 4A together with the magnetization curves shown in FIGURES 5A, 5B, 5C and 5D. Since FIGURES 1 through 4 differ only in operating condition, similar elements are identified by the same reference numerals. Referring now to FIG- URE 1, a ferromagnetic core 10 is provided with intersecting transverse openings or passageways 11 and 12. The core is thus provided with four legs or common regions 13, 14, 15 and 16, and end or cap regions 17 and 18 which join the legs with a mass of ferromagnetic material. A first winding 19 is wound around the cap region 18 through the opening 11 while a second winding 20 is wound around the cap region 17 through the opening 12.

The following explanation will discuss the operation of the device in its simplest form, that is, where an alternating current is applied to one winding, for example, the winding 19, and a direct current is applied to the winding 20, the unidirectional flux generated by the current in the winding 20 controlling the permeability of the path followed by the flux generated by the alternating current in the winding 19. It should be understood, however, the other combinations of currents could be used as explained above and as further explained below. In this specification, the winding in the circuit being controlled 'will for convenience often be called the load winding while the winding in the circuit effecting the control will be called the control winding.

As shown in FIGURES 1 and 1A, the magnetic circuit of the unidirectional flux generated by the direct current in the winding 20, indicated by the solid arrows, the solid dots and the Xs surrounded by a single circle, includes two paths. The first of these paths is through the end region 17, the leg 16, the end region 18 and the leg 15 while the second is through the end region 17, the leg 13, the end region 18 and the leg 14. The magnetic circuit of the alternating flux, indicated by the broken arrows, the open dots and the Xs surrounded by a double circle, generated as a result of the alternating current in the winding 19 also includes two paths; a first path through the end region 17, the leg 14, the end region 18 and the leg 15, and a second path through the end region 17, the leg 13, the end region 18 and the leg 16.

Of course, in each of the legs or common regions, there is only one flux having alternating and unidirectional components. However, for purposes of clarity in discussing the invention, these flux components will sometimes in this specification be referred to simply as fluxes. As can be seen, on the first half cycle of the alternating current, the unidirectional flux component and the alternating flux component are in additive relationship in the 'legs 13 and 15 but are in opposing relationship in the legs 14 and 16. Consequently, the permeability of the legs 14 and 16 is much greater than the permeability in the legs 13 and 15 and the reluctance in the legs 14 and 16 is lower than the reluctance in the legs 13 and 15. Of course, on the second half cycle of the alternating current, the flux components will be in opposition in the legs 13 and 15 and adding in the legs 14 and 16. On either half cycle, however, each alternating flux path will contain one additive leg and one subtractive leg. As the result of the additive flux components in the leg 15 and the subtractive flux components in the leg 14, the average permeability of the first path followed by the alternating flux is reduced and consequently the average inductance of the winding 19 is reduced. The average permeability of the second path followed by the alternating flux is also reduced because this path also includes one common region in which the flux components are in opposition and a second common region in which they are in additive relationship. The average permeability of each path followed by the alternating flux is thus reduced and consequently the average inductance of the winding 19 is reduced. The core is preferably made symmetrical so that its operation will be identical on each half cycle of the alternating current.

In FIGURES i2 and 2A, the direct current applied to the winding 20 has been increased with the result that more unidirectional flux is generated in the core. As a result of this increase in unidirectional flux, the legs and 13 have an even lower permeability than was the case in FIGURE 1 and their reluctances are correspondingly higher. Some of the alternating flux passing from the leg 14 to the leg 15 may seek out paths of lesser reluctance and thus all of it may not follow a relatively straight line from the leg 14 to the leg 15 but rather some will fringe out to the central portion of the end region 18. Other known but not completely understood phenomena of magnetic circuits such as the availability and magnetizability of magnetic domains will also contribute to this fringing effect. Since the flux which fringes out in this manner will cut the winding in equal magnitudes but opposite directions, only a very small effective flux linkage is present between the winding 19 and the winding 20 and good isolation is maintained between them.

In FIGURES 3 and 3A, a third winding 21 has been Wound around the end region 17 through the opening 12 so that its axis is parallel to the axis of the winding 20. This winding 21 acts as a secondary winding with the result that the device now acts as a variable transformer as a result of the varying inductance phenomena discussed above. As pointed out above, as the unidirectional flux in the core increases, the reluctance of the legs 13 and 15 get higher and higher and their permeability gets lower and lower. As pointed out above, the reluctance of a magnetic circuit is dependent both on its length and on its permeability. As the permeability of the leg 15 gets lower and lower, the reluctance of the magnetic path between the leg 14 and the leg 16 becomes less than the reluctance of the magnetic path between the leg 14 and the leg 15. Consequently, some of the flux leaving the leg 14 crosses over the end portion 18 and passes into the low reluctance portion of the leg 16.

This crossover flux cuts the winding 21 with the result that a voltage is induced therein. The crossover flux also cuts the winding 20 and induces a voltage in the winding; however, this voltage can be essentially eliminated by use of a suitable choke. It should be understood that there is no particular point in which the flux from the leg 14 crosses over to the leg 16 instead of going to the leg 15 but that rather this is a gradual process with more and more flux crossing over as the reluctance of the leg 15 gets higher and higher and that of leg 16 gets lower and lower. As previously pointed out, however, it appears that the greatest amount of energy transfer is due to the varying inductance phenomena and only to a limited degree to the action of the crossover flux.

It should be understood that if desired the functions of the control winding 20 and the secondary winding 21 can be combined in a single winding to which is applied a DC bias or control signal and from which the output is taken.

FIGURES 4 and 4A illustrate the operation of the device in the nonfrequency doubling mode. In these figures, a primary bias winding 22 has been wound through the opening 11 and acts to generate a unidirectional flux in the paths followed by the alternating flux. If the level of the bias flux generated by the winding 22, indicated by the dotted arrows, the double Xs and the double circles, is maintained higher than the maximum value the alternating flux attains, the inductance of the secondary winding is only maximized once each cycle with the result that no frequency doubling occurs.

Looking at FIGURES 4 and 4A from the crossover flux standpoint, it can be seen that the legs 14 and 16 will always be the low reluctance legs and consequently the crossover flux will always follow the path shown with the result that the voltage induced in secondary winding 21 will have the same frequency as the input to primary winding 19 as explained previously.

It may be helpful at this point to turn to FIGURES 5A, 5B, 5C and 5D to further an understanding of the principles of operation of the present invention. When no control or DC current flows in the winding 20, all of the magnetic legs 13, 14, 15 and 16 are unbiased from a magnetic standpoint and each leg operates at substantially the same point on its associated hysteresis loop since the magnetic flux in each leg is essentially identical in magnitude for all values of load current, i.e., the current through the winding 19, the only difference being that two legs will be operating on the negative portion of their hysteresis loops while the other two legs are operating on the positive portion of their loops. Therefore, in the practical case where the load current is supplied from an alternating current source, the locus of the operating points associated with each leg will be essentially identical and will trace out a pattern similar to that shown in FIGURE 5A for a complete cycle of load current. This curve is what is normally referred to as a normal operating hysteresis loop. In this case the load current will see vva near maximum average inductance over the entire cycle because there is no magnetic biasing in any of the legs and thus each leg has its maximum or near maximum permeability. Each of these curves can be experimentally verified by means of hysteresisograph waveforms viewed upon an oscilloscope.

Let it now be assumed that a direct current is passed through the winding 20 with the result that a magnetic bias is established in each leg. This bias is indicated by the vertical dotted lines in FIGURES 5B and 5C. The hysteresis curve associated with the additive legs 13 and 15 is now similar to that shown in FIGURE 5B While the hysteresis curve associated with the subtractive legs 14 and 16 is similar to that shown in FIGURE 5C. As can be seen from these figures, each of these hysteresis curves makes it swing around the bias level. The composite hysteresis loop associated with the legs 14 and 15, that is, with the first path followed by the alternating flux is similar to that shown in FIGURE 5D. This hysteresis loop is made up primarily of the left side of the curve of FIGURE 5B and the right side of the curve of FIGURE with the bias level set by the control current acting as the midpoint of the curve in each part of the curve.

The shape of the curve in FIGURE 5D will be effected mainly by the leg having the highest permeability at any given time. This is, of course, only completely true if the permeability of one of the legs is very high compared to the other and thus becomes more the case for the load winding as the control current magnitude is increased to a high value. Because of the symmetry of the core in the preferred case, the average permeability of the material associated with leg 14 will be higher than that of leg 15 during one-half of the cycle of the load current, and vice versa during the other half cycle. This symmetry, in conjunction with the operation of the leg paths causes the hysteresis loop of FIGURE 5D to have its different characteristic shape and results in the load current seeing an average inductance over its cycle that is less than it saw when there was no control current. This is evident as the hysteresis loop of FIGURE 5D has effectively rotated somewhat clockwise as compared to the hysteresis loop of FIGURE 5A. A larger H on the average is now required for a specific value of B as the hysteresis loop effectively rotates clockwise.

As the control current is still further increased, the hysteresis loop is effectively rotated further and further clockwise until it is essentially horizontal. This indicates that the average permeability associated with the material linked by the load winding is very low compared to the no control current condition and, of course, in this case the variable inductance has a very low average inductance. This is the saturated condition for the inductor of the present invention since additional control current will cause a relatively small change in the average inductance that the load current will see over its cycle of operation.

A typical plot of the inductance of the load winding as a function of the control current is shown in FIGURE 6. As will be evident from the figure and from the previous discussion, the polarity of the control current is unimportant to the control of the device.

FIGURES 7, 8 and 9 illustrate other core structures that could be used for either the variable inductor or the variable transformer of the present invention. As shown, they illustrate variable inductors; however, it will be obvious that a secondary winding could be added to convert their operation to that of a variable transformer as explained about. In FIGURE 7, a pair of C cores 2'5 and 26 are rotated 90 from each other and their bases joined together. The base of each C core 25 and 26 is preferably lapped very smooth so that the junctions of the cores are as perfect as possible and the presence of any air gap is minimized. A first winding 27 is wound on the core 25 while a second winding 28 is wound on the core 26. The common regions which the fiuxes generated by both of the coils 27 and 28 traverse are shown generally at 29, 30 and 3-1. The fourth common region is, of course, at the other, hidden, junction of the cores 25 and 26. This then is a case where the legs have no structurally definable existence but in which they nevertheless have operative existence. The windings 27 and 2 8 are shown with their axes at right angles. This is perferable but not essential as the required flux paths will still be set up in the cores even if the coils are not at right angles. However, when the coils are not at right angles, the coupling between them is increased and thus the isolation of each coil from the other is not maximized.

The core of FIGURE 8 is very similar to that of FIG- URES 1 through 4 and is constructed by forming slots 32 in C cores 33 and 34 similar to the cores 25 and 26 of FIGURE 7. The bases of the cores 33 and 34 are then lapped and joined together to form a structure with four legs or common regions 35, 3'6, 3 7 and 38. A winding 39 is wound on the core 33 and a winding 40 is wound on the core 34, preferably with their axes at right angles but not necessarily.

FIGURE 9 shows a tubular ferromagnetic core 41 having an axial passageway 42 and a pair of oppositely disposed radial slots 43 and 44. A first winding 45 is wound through the axial passageway 42 while a second winding 46 is wound through the slots 43 and 44. The fluxes generated by these two windings will have common regions at 47 and 48 and the similar areas on the opposite side of the core.

FIGURE 10 shows a half-wave rectifier utilizing a variable inductor constructed in accordance with the present invention. In this figure, the inductor 53 has its load winding 54 connected in series with an AC power supply 55 and load 56. The control winding -7 of the inductor '53 is connected in series with a rectifying element such as a diode 58 across the AC power supply 55. In operation, during one-half cycle of the output of the power supply 55, the diode 58 will conduct and a unidirectional current will flow through the winding 5'7 causing a unidirectional flux to be generated in the core of the inductor 53 with the result that the impedance of the winding 54 is reduced and a substantial current flows through the load 56. However, on the other half cycle of the AC power supply, no current will flow through the winding 57 with the result that there will be no unidirectional flux generated in the core of the inductor 53 and the winding 54 will have its maximum inductance and impedance. Consequently, only a relatively small current will flow through the load 56 on this half cycle. Thus, current of a substantial magnitude will flow to the load 56 only on alternate half cycles of the output of the power supply 55. In many instances, this circuit will be superior to a conventional half-wave rectifying circuit because it can be provided with great power handling capacity wherein the conventional half-wave rectifier has a power capacity limited by the rectifier element. In the circuit of the present invention, the current flow through the diode 58 can be limited to a reasonably small value by providing the shunt circuit of which it is a part with a relatively high resistance thereby permitting the use of a less expensive, lower power diode.

If desired, the inductor of the present invention can also be used in a rectifying circuit where the load circuit is conductively isolated from the input circuit. Such a circuit is shown in FIGURE 11. In this figure, a variable inductor 59 of the type previously described is provided with a load winding 60 which is coupled in series with a load 61 and the secondary 62 of a conventional transformer 63. The control winding 64 of the inductor '59 is connected in series with a diode 65 across an AC power supply 66, the output of which is also applied to the primary winding 67. of the transformer 63. The operation of this circuit is similar to the operation of the circuit of FIGURE 10, the only exception being that the transformer 63 serves to conductively isolate the load 61 from the power supply 66.

FIGURE 12 shows a full-wave rectifier utilizing a pair of the variable inductors of the present invention. In this figure, a first variable inductor 68 of the type described has a load winding 69 connected between one end of the secondary winding 70 of the conventional transformer 71 and one terminal of a load 72. A control winding 73 of the induct-or 68 is connected in series with a diode 74 across the output of an AC power supply 7 5. The output of the AC power supply is also applied across the primary winding 76 of the transformer 71. A second variable inductor 77 of the type described has a load winding 78 connected in series between the other end of the secondary 70 and the first terminal of the load 72. The other terminal of the load 72 is connected to a center tap of the secondary winding 70. The control winding 79 of the inductor 77 is connected in series with a rectifier 80 across the output of the power supply 75.

The diodes 74 and 80 are poled in opposite directions so that a current flows through the control winding 73 of the inductor 68 during the first half cycle of the output of the power supply and through the control winding 79 of the inductor 77 during the other half cycle of the output of the power supply. It can thus be seen that the load winding 69 will have a low impedance during the first half cycle of the output of power supply 75. The load winding 78, on the other hand, will have a high impedance during the first half cycle and a low impedance during the second half cycle. The current in the secondary Winding 70 will thus choose to flow through load winding 69 during the first half of the cycle of the voltage appearing across the primary winding 76 and through load winding 78 during the second half cycle of this voltage and will consequently always flow through the load 72 in the same direction.

FIGURE 13 shows a DC to AC power converter employing the variable inductor of the present invention. In this figure, the load winding of a variable inductor 91 is connected in series with a DC power supply 92 and a load 93. An oscillator amplifier 94 receives power from the DC power supply 92 and supplies an alternating current signal to the control winding 95 of the inductor 91. As the flux linking the turns of the load winding 90 is varied as a function of the fluctuation of the AC flux component in the core, a voltage will be induced in the winding 90 and will cause an AC voltage component to be superimposed upon the DC voltage and appear across the load 93. It can be seen that although the functions of the direct current and the alternating current are reversed in this circuit, the basic principle of operation remains the same. The various legs of the core are caused to have a changing permeability and reluctance by the presence of an alternating flux. Here, instead of the changing permeability and reluctance being utilized to change the average inductance of the alternating current winding, it is used to vary the flux linking the direct current winding and thereby induce a voltage therein. This 13 circuit thus makes use in the load circuit of the variation of the inductance to induce an AC current across the output winding.

Turning now to FIGURE 14, there is shown an amplifier employing the variable inductor of the present invention in the same fashion as does the converter of FIG- URE 13. In this circuit, the load winding 96 of the variable inductor 97 is connected in series with a DC power supply 98 and a resistor 99, the output of the amplifier being taken across the resistor 99. The control winding 100 of the variable inductor is connected to the source of signals to be amplified. As was the case in FIGURE 12, the variations of the alternating flux component in the core of the inductor 97 resulting from the fluctuations in current passing through the coil 100' will cause a corresponding variation in the inductance of Winding 96 with the result that an alternating voltage will be induced in the winding 96 and the voltage appearing across the resistor 99 will be an amplified version of the input to the winding 100.

FIGURE 15 shows a frequency quadrupler formed by cascading two frequency doubling circuits utilizing variable transformers of the present invention. An input signal is applied to the primary 106 of a variable transformer 107 and, in the presence of a suitable direct current in control winding 108, appears doubled in frequency across the secondary 109 of variable transformer 107. The voltage appearing across secondary 109 also appears across the primary 110 of a secondary variable transformer 111 and will again be doubled in frequencyso as to appear as a quadruple frequency output across the secondary 112 of transformer 111, assuming, of course, that a suitable control current is present in the control winding 113 of variable transformer 111. The control voltage for both variable transformers 107 and 111 is obtained by rectifying the output appearing across secondary winding 112 in a half-wave rectifier 114, the output of which is filtered by a capacitor input filter comprising filter capacitor 115 and resistor 116, with a variable DC voltage tapped by potentiometer 117 for application to the control windings 108 and 113 which are connected in parallel. The control voltage could be taken from the primary winding if desired, however, it is preferable to take the control from the last output winding because the higher frequency reduces ripple and gives a better DC signal.

FIGURE 16 shows an improved power supply utilizing the variable transformer of the present invention in its frequency doubling mode of operation. The unregulated input AC voltage is applied across input terminal 221 and appears across the primary winding 222 of a variable transformer 223. If a suitable control current is present in the control winding 224 of the variable transformer 223, a double frequency output voltage will be developed in the secondary winding 225. The secondary voltage may be stepped up or stepped down from the primary voltage by employing an appropriate turns ratio, as in the case of prior art transformers. In choosing the turns ratio, however, a correction must be made to take into account the flux that does not cross over but follows the normal paths. Assuming that the turns ratio is set for voltage step up, which is customary in many power supply trans formers, then the voltage developed in secondary winding 225 will be doubled in frequency and greater in magnitude than the input voltage across primary winding 222.

The secondary winding 225 is center tapped with the center tap being grounded and the ends being connected to diodes 226 and 227, both of which are coupled to a filter circuit comprising inductance 228 and filter capacitor 229. This circuit is a full-wave rectifier circuit well known to those skilled in the art, and the output thereof is a direct current voltage approximately equal to the RMS value of he AC voltage developed across one-half of the secondary winding. The DC output voltage is regulated by a feedback circuit which derives the control voltage from the output voltage of the rectifier. The feedback circuit comprises an NPN transistor 230 connected with its collector-emitter circuit in parallel with the control winding 224. The base level of transistor 230, which controls the impedance of the collector-emitter circuit therein, is derived from potentiometer 231 connected in parallel with the output of the rectifier. Resistor 232 is the output resistor for the transistor 230 and the resistor 223 is a current limiting resistor for the control Winding 224.

In the operation of the feedback circuit, potentiometer 231 is adjusted to give the desired output voltage level from the rectifier. The voltage level at the tap of potentiometer 231 sets the bias of transistor 230, which in turn controls the internal impedanc of the collector-emitter path and thus sets the voltage applied across the control winding 224. If the output voltage of the rectifier drops from its initial value, either through a drop in the line voltage applied to the primary 222 or through an increase in the load on the rectifier, the base level of transistor 230 is correspondingly lowered, and the impedance of its collector-emitter path is increased, thereby raising the voltage applied to the control winding, which increases the control unidirectional flux and causes an increase in the crossover flux with the result that a higher voltage is induced in secondary winding 225 to counteract the drop. If the output voltage of the rectifier tends to rise, the voltage applied to the control winding is lowered by the same process to counteract the rise.

This power supply circuit provides two notable improvements over prior art power supply circuits, the first being a decrease in the percentage in ripple in the DC output due to the frequency doubling within the variable transformer and the second being the use of the variable transformer as an output voltage control and an output voltage regulator. In the prior art power supplies, output voltages were controlled by means of variable impedances in series with the flow of energy through the circuit. The circuit of FIGURE 16 also employs a variable impedance as an output voltage control, but since the variable impedance is in the control circuit rather than in the primary or secondary circuits, no appreciable power is consumed therein, as was the case in the prior art voltage controls. Therefore, the variable resistance in this circuit can be quite small even though large amounts of energy are transferred between the primary and secondary circuits, whereas in the prior art voltage contros this was impossible because the variable element was in the high energy transfer path. Although this voltage regulating circuit has been described in connection with the frequency doubling mode of the variable transformer of the present invention, it should be obvious that the variable transformer can be used in its nonfrequency doubling mode as well although the size of the filter will have to be increased.

FIGURES 17A, 17B and 17C show schematically various cores in which the windings are generated such that their axes are not transverse. The positioning of the various legs or common regions in these figures is believed to be obvious and not to warrant extended discussion. Of course, the winding may also be wound nontransversely on the other cores illustrated as such as desired.

When reference is made in the claims to the magnetic circuit encompassed by a winding being nonsaturated, this is not intended to imply that all portions of the core remain nonsaturated. Further, the term average inductance has been used interchangeably with and to mean the same as effective inductance.

What is claimed is:

1. A half-wave rectifying system comprising: a magnetic core having four common regions and two end regions magnetically joining said common regions, a load winding wound on said core between the first and fourth and the second and third of said common regions, a control winding wound on said core between the first and second and third ahd fourth common regions; a source of alternating current; a load; means connecting said source, said load winding and said load in an electric circuit; a diode; mans connecting said diode and said control winding across said source to supply control current to said control winding on alternate half cycles of said alternating current, the presence of control current in said control winding causing the inductance of said load winding to be low and the absence of control circuit in said control winding causing the inductance of said load winding to be high.

2. The system of claim 1 wherein said means connecting said source, said load winding and said load in an electric circuit includes a transformer.

3. A half-wave rectifying system comprising: a source of alternating current; a load; a magnetic core having four common regions and first and second portions joining said four common regions; a first winding wound on said core with its axis extending between said first and second common regions and between said third and fourth common regions; means connecting said source, said first winding and said load in a series circuit whereby an alternating current may be passed through said first winding and an alternating magnetic flux generated in said core; a second Winding wound on said core with its axis extending between said first and fourth common regions and between said secnod and third common regions; a diode; means connecting said diode and said second winding across said alternating current source whereby a unidirectional current is passed through said second winding during each alternate half cycle of said alternating current and a unidirectional magnetic flux is generated in said core during said alternate half cycles, said unidirectional flux acting on the magnetic circuit encompassed by said first winding such that the average permeability of said magnetic circuit is increased and the average inductance of said first winding is decreased during said alternate half cycles.

4. A half-wave rectifying system comprising: an alternating current source; a load; a magnetic core; a first winding wound on said core, said first winding being connected in series with said source and said load whereby alternating current may be passed through said first winding and an alternating magnetic flux generated in said core, said alternating flux following first and second paths in said core; a second winding wound on said core; a diode; means connecting said second winding and said diode across said alternating current source whereby a unidirectional current is passed through said second winding on alternate half cycles of said alternating current, said unidirectional current passing through said second winding generating a unidirectional magnetic flux in said core, said unidirectional flux following third and fourth paths in said core; said first path sharing a first common region in said core with said third path and a second common region in said core with said fourth path, said second path sharing a third common region in said core with said third path and a fourth common region in said core with said fourth path, said fluxes being in opposing relationship in two of said common regions whereby the reluctance of said common regions is reduced, and in additive relationship in the other two of said common regions whereby the reluctance of said other two common regions is increased, each of said, first, second, third and fourth paths including one opposing flux common region and one additive flux common region whereby the average permeability of each of said first and second paths is increased and the average inductance of said first winding is decreased during said alternate half cycles.

5. A half-wave rectifying system comprising: a source of alternating curernt; a load; a transformer having a primary winding and a secondary winding; means connecting said primary winding to said source of alternating current; a magnetic core having four common regions and first and second portions joining said four common re- 16 gions; a first winding wound on said core with its axis extending between said first and second common regions and between said third and fourth common regions; means connecting said secondary winding, said first winding and said load in a series circuit whereby an alternating current may be passed through said first winding and an alternating magnetic flux generated in said core; a second winding wound on said core with its axis extending between said first and fourth common regions and between second and third common regions; a diode; means connecting said diode and said second winding across said alternating current source whereby a unidirectional current is passed through said second widing during each alternate half cycle of said alternating current and a unidirectional magnetic flux is generated in said core during said alternate half cycles, said unidirectional flux acting on the magnetic circuit encompassed by said first winding such that the average'permeability of said magnetic circuit is increased and the average inductance of said first winding is decreased during said alternate half cycles.

6. A half-wave rectifying system comprising: a source of alternating current; a load; a transformer having a primary winding and a secondary winding; means connecting said primary winding to said source of alternating current; a magnetic core; a. first winding wound on said core; means connecting said secondary winding, said first winding and said load in a series circuit whereby an alternating current may be passed through said first winding and an alternating magnetic flux generated in said core, said alternating flux following first and second paths in said core; a second winding wound on said core; a diode; means connecting said diode and said second winding across said alternating current source whereby a unidirectional current is passed through said second Winding during each alternate half cycle of said alternating current, said unidirectional current passing through said second winding generating a unidirectional magnetic flux in said core, said unidirectional flux following third and fourth paths in said cores; said first path sharing a first common region in said core with said third path and a second common region in said core with said fourth path, said second path sharing a third common region in said core with said third path and a fourth com-mon region in said core with said fourth path, said fluxes being in opposing relationship in two of said common regions whereby the reluctance of said common regions is reduced, and in additive relationship in the other two of said common regions whereby the reluctance of said other two common regions is increased, each of said first, second, third and fourth paths including one opposing flux common region and one additive flux common region whereby the average permeability of each of said first and second paths is increased and the average inductance of said first winding is increased during said alternate half cycles.

7. A full-Wave rectifying system comprising: first and second magnetic cores each having four common regions and two end regions magnetically joining said common regions, a load winding Wound on the core between the first and fourth and second and third of said common regions, a control winding wound on the core between the first and second and third and fourth comrnon regions; a source of alternating current; a transformer haw other end of said secondary winding and said first ter-' minal of said load; a second diode; means connecting said second diode and the control winding of said second core across said alternating current source to supply control current to said control winding on negative half cycles of said alternating current; and means connecting the other terminal of said load to the midpoint of said secondary winding; the presence of control current in the control winding of one of said cores causing the inductance of the load winding of the core to be low and the absence of control current in the control winding of one of the cores causing the inductance of the load winding of the core to be high.

8. A full-wave rectifying system comprising: a source of alternating current; a transformer having primary and secondary windings; a load; means connecting said primary winding to said source of alternating current; a first magnetic core having four common regions and first and second portions joining said four common regions; a first winding wound on said first core with its axis extending between said first and second common regions and between said third and fourth common regions; means connectlng said first winding of said first core in series between one end of said secondary winding and one terminal of said load whereby an alternating current may be passed through said first winding of said first core and an alternating magnetic flux generated in said first core; a second winding wound on said first core with its axis extending between said first and fourth common regions and between said second and third common regions; a first diode; means connecting said first diode and said second winding of said first core across said alternating current source whereby a unidirectional current is passed through said second winding of said first core during each alternate half cycle of said alternating current and a unidirectional magnetic flux is generated in said core during said alternate half cycles, said unidirectional flux acting on the magnetic circuit encompassed by said first winding of said first core such that the average permeability of said magnetic circuit is increased and the average inductance of said first winding is decreased during said alternate half cycles; a second magnetic core having four common regions and first and second portions joining said four common regions; a first winding wound on said second core with its axis extending between said first and second common regions and between said third and fourth common regions; means connecting said first winding of said second core in series between the other end of said secondary winding and said first terminal of said load whereby an alternating current may be passed through said first winding and an alternating magnetic flux generated in said second core; a second winding wound on said second core with is axis extending between said first and fourth common regions and between said second and third common regions; a second diode; means connecting said second diode and said second winding of said second core across said alternating current source whereby a unidirectional current is passed through said second winding of said second core during the remaining half cycles of said alternating current and a unidirectional magnetic flux is generated in said second core during said remaining half cycles, said unidirectional flux acting on the magnetic circuit encompassed by said first winding of said second core such that the average permeability of said magnetic circuit of second core is increased and the average inductance of said first winding of said second core is decreased during said remaining half cycles; and means connecting the other terminal of said load to the midpoint of said secondary winding.

9. A full-wave rectifying system comprising: a source of alternating current; a transformer having primary and secondary windings; a load; means connecting said primary winding to said source of alternating current; a first magnetic core; a first winding wound on said core; means connecting said first winding of said first core in series between one end of said secondary winding and one terminal of said load whereby an alternating current may be passed through said first winding of said first core and an alternating magnetic flux generated in first core, said alternating flux following first and second paths in said first core; a second winding wound on said first core; a first diode; means connecting said first diode and said second winding of said first core across said alternating current source whereby a unidirectional current is passed through said second winding of said first core on alternate half cycles of said alternating current, said unidirectional current passing through said second winding generating a unidirectional magnetic flux in said core, said unidirectional flux following third and fourth paths in said core; said first path sharing a first common region in said core with said third path and a second common region in said core with fourth path, said second path sharing a third common region in said core with said third path and a fourth common region in said core with said fourth path, said fluxes being in opposing relationship in two of said common regions whereby the reluctance of said common regions is reduced, and in additive relationship in the other two of said common regions whereby the reluctance of said other two common regions is increased, each of said first, second, third and fourth paths including one opposing flux common region and one additive flux common reglon whereby the average permeability of each of said first and second paths is increased and the average inductanceof said first winding of said first core is decreased during said alternate half cycles; a second magnetic core; a first winding wound on said second core; means connectlng said first winding of said second core in series between the other end of said secondary winding and said first temrinal of said load whereby an alternating current may be passed through said first winding and an alternating flux generated in said second core, said alternating flux following first and second paths in said second core; a second winding wound on said second core; a second diode; means connecting said second diode and second winding of said second core across said alternating current source whereby a unidirectional current is passed through said second winding of said second core during the remaining half cycles of said alternating current, said unidirectional current passing through said second Winding of said second core generating a unidirectional magnetic flux in said second core, said unidirectional flux following third and fourth paths in said second core; said first path sharing a first common region in said second core with said third path and a second common region in said second core with said fourth path, said second path sharing a third common region in said second core with said third path and a fourth common region in said second core with said fourth path, said fluxes being in opposing relationship in two of said common regions whereby the reluctance of said common regions is reduced, and in additive relationship in the other two of said common regions is increased, each of said first, second, third and fourth paths including one opposing flux common region and one additive fiux common region whereby the average permeability of each of said first and second paths is increased and the average inductance of said first winding of said second core is decreased during the remaining half cycles; and means connecting the other terminal of said load to the midpoint of said secondary winding.

10. A DC to AC converter system comprising: a magnetic core having four common regions and two end regions magnetically joining said common regions, a load winding on said core between the first and fourth and the second and third of said common regions, a control winding wound on said core between the first and second and third and fourth common regions; a source of direct current; a load; means for producing an alternating current signal; means connecting said load winding between said DC source and said load; means coupling said control winding to said means for producing an alternating current signal to supply control current to said control winding, variations in said control current causing variations in the voltage across said load.

11. A DC to AC conversion system comprising: a source of direct current; a load; an oscillator for producing an alternating current signal; a magnetic core having four common regions and first and second portions joining said four common regions; a first winding wound on said core with its axis extending between said first and second common regions and between said third and fourth common regions; means connecting said first winding between said DC source and said load whereby a direct current is passed through said first winding and a unidirectional magnetic flux is generated in said core; a second winding wound on said core with its axis extending between said first and fourth common regions and between said second and third common regions; means coupling said second winding to said oscillator whereby an alternating current is passed through said second Winding and and alterating magnetic flux is generated in said core, said alternating flux acting to vary the average permeability of the magnetic circuit encompassed by said first winding and the average inductance of said first winding whereby an alternating voltage is induced in said first winding.

12. A. DC to AC conversion system comprising: a source of direct current; a load; an oscillator for producing an alternating current signal; a magnetic core; a first winding wound on said core; means connecting said first winding in series with said direct current source and said load whereby a direct current is passed through said first winding and a unidirectional magnetic flux is generated in said core, said unidirectional flux following first and second paths in said core; a second winding wound on said core; means coupling said second winding to said oscillator whereby an alternating current is passed through said second winding and an-alternating magnetic flux is generated in said core, said alternating flux following third and fourth paths in said core; said first path sharing a first common region in said core with said third path and a second common region in said core with said fourth path, said second path sharing a third common region in said core with said third path and a fourth common region in said core with said fourth path, said fluxes being in opposing relationship in two of said common regions whereby the reluctance of said common regions is reduced, and an additive relationship in the other two of said common regions whereby the reluctance of said other two common regions is increased, each of said first, second, third and fourth paths including one opposing flux common region and one additive flux common region whereby the average permeability of each of said first and second paths and the average inductance of said first winding are varied in accordance with said alternating current signal whereby an alternating voltage is induced in said first winding.

13. A DC to AC conversion system comprising: a source of direct current; a load; an oscillator for producing an alternating current signal; a magnetic core having four symmetrical legs and first and second portions joining said four legs; a first winding wound on said core; means connecting said first winding in series with said source of direct current and said load whereby a direct current is passed through said first winding and a unidirectional magnetic flux is generated in said core, said unidirectional flux following a first path through said first portion, said first leg, said second portion, and said fourth leg, and a second path through said first portion, said second leg, said second portion and said third leg; a second winding wound on said core; means coupling said oscillator to said second winding whereby an alternating cur rent is passed through said second winding, said alternating current passing through said second winding generating an alternating magnetic flux in said core, said alternating flux following a third path through said first portion, said first leg, said second portion and said second leg and a fourth path through said first portion, said fourth leg, said second portion and said third leg; said fluxes being in opposing relationship in said first and third legs and in additive relationship in said second and fourth legs during the first half cycle of said alternating current, and in opposing relationship in said second and fourth legs and in additive relationship in said first and third legs during the second half cycle of said alternating current whereby on either half cycle of said alternating current each of said first and second paths includes one opposing flux leg and one additive flux leg whereby the average permeability of each of said first and second paths and the average inductance of said first winding is varied in accordance with said alternating current signal whereby an alternating voltage is induced in said first winding.

14. An amplifier comprising: a magnetic core having four common regions and two end regions magnetically joining said common regions, a load winding wound on said core between the first and fourth and the second and third of said common regions, a control winding wound on said core between the first and second and third and fourth common regions; a source of direct current; load means; means coupling said load winding to said source and said load means; a source of signals to be amplified; means coupling said control winding with said source of signals to supply control current to said control winding, variations in said control current causing corresponding variations to occur in the voltage across said load means.

15. An amplifier comprising: a source of direct current; load means; a magnetic core having four common regions and first and second portions joining said four common regions; a first winding wound on said core with its axis extending between said first and second common regions and between said third and fourth common regions; means coupling said first winding to said source and said load means whereby a direct current is passed through said first winding and a unidirectional magnetic flux is generated in said core; a second winding wound on said core with its axis extending between said first and fourth common regions and between said second and third common regions; a source of signals to be amplified; means coupling said second winding with said source of signals to be amplified for applying an alternating current electrical signal to said second winding whereby an alternating magnetic flux is generated in said core, said alternating flux acting to vary the average permeability of the magnetic circuit encompassed by said first winding and the average inductance of said first winding whereby an alternating voltage is induced in said first winding corresponding to said signals to be amplified.

16. An amplifier comprising: a source of direct current; a load; a magnetic core; a first winding wound on said core; means connecting said first winding in series with said source and said load, current passing through said first winding generating a unidirectional magnetic fiux in said core, said unidirectional flux following first and second paths in said core; a second winding wound on said core; a source of signals to be amplified; means for coupling said second winding to said source of signals to be amplified whereby an alternating current is passed through said sceond winding and an alternating magnetic flux is generated in said core, said alternating flux following third and fourth paths in said core; said first path sharing a first common region in said core with said third path and a second common region in said core with said fourth path; said second path sharing a third common region in said core with said third path and a fourth common region in said core with said fourth path, said fluxes being in opposing relationship in two of said common regions whereby the reluctance of said common regions is reduced, and in additive relationship in the other two of said common regions whereby the reluctance of said other two common regions is increased, each of said first, second, third and fourth paths including one opposing flux common region and one additive flux common region whereby the average permeability of said first and second paths and the effective inductance of said first winding vary in accordance with said alternating current whereby an alternating voltage is induced in said first winding; corresponding to said signals to be amplified.

17. An amplifier comprising: a source of direct current; a load; a magnetic core having four symmetrical legs and first and second portions joining said four legs; a first winding wound on said core; means connecting said first winding in series with said source and said load, current passing through said first winding generating a unidirectional magnetic flux in said core; said unidirectional flux following a first path through said first portion, said first leg, said second portion and said fourth leg, and a second path through said first portion, said second leg, and a second portion, .and said third leg; a second winding wound on said core; a source of signals to be amplified; means coupling said second winding to said source of signals to be amplified whereby an alternating current is passed through said second winding and an alternating magnetic flux is generated in said core, said alternating flux following a third path through said first portion, said first leg, said second portion and said second leg and a fourth path through said first portion, said fourth leg, said second portion and said third leg; said fluxes being in opposing relationship in said first and third legs and in additive relationship in said second and fourth legs during the first half cycle of said alternating current, and in opposing relationship in said second and fourth legs and in additive relationship in said first and third legs during the second half cycle of said alternating current whereby on either half cycle of said alternating current each of said first and second paths includes one opposing flux leg and one additive fiux leg whereby the average permeability of each of said first and second paths and the effective inductanceof said first winding vary in accordance with said alternating current whereby an alternating voltage is induced in said first winding corresponding to said signals to be amplified.

18. A frequency quadrupling system comprising: first and second magnetic cores each having four common regions and two end regions magnetically joining said common regions, a primary winding wound on said core between the first and fourth and the second and third of said common regions, a secondary winding, a control winding, said secondary and control windings being wound on said core between said first and second and said third and fourth common regions; an input circuit; an output circuit; a source of AC. voltage coupled to said input circuit; means coupling the primary winding of said first core to said input circuit; means coupling the secondary winding of said first core to the primary winding of said second core; means coupling the secondary winding of said second core to said output circuit; and means for supplying a control current to the control windings of said first and second cores.

19. The system of claim 18 wherein said control current supplying means includes rectifying means coupled across said output circuit.

20. A frequency quadrupling system comprising: an input circuit; and output circuit; a source of AC voltage; means coupling said source to said input circuit; a magnetic core having four common regions and first and second portions joining said four common regions; a first winding wound on said core with its axis extending between said first and second common regions and between said third and fourth common regions; means coupling said first winding to said input circuit whereby an alternating current is passed through said first winding and an alternating magnetic flux is generated in said core; a second winding Wound on said core with its axis extending between said first and fourth common regions and between said second and third common regions; a source of direct current; means coupling said source of direct current to said second winding, direct current passing through said second winding generating a unidirectional magnetic flux in said core; a third winding wound on said core with its axis extending between said first and fourth common regions and between said second and third common regions; means coupling said third winding to said output circuit; said unidirectional flux generated by said second winding interacting with said alternating flux generated by said first winding to develop a voltage in said third winding, the magnitude of said developed voltage being controlled by the magnitude of said unidirectional flux; a second magnetic core having four common regions and first and second portions joining said common regions; a first winding wound on said second core with its axis extending between said first and second common regions and said third and fourth common regions; means coupling said first winding of said second core to said output circuit whereby an alternating current is passed through said first winding of said second core and an alternating mag netic flux is generated in said second core; a second winding wound on said second core with its axis extending between said first and fourth common regions and said second and third common regions; means for supplying direct current to said second winding of said second core whereby a unidirectional magnetic flux is generated in said second core; a third winding wound on said second core with its axis extending between said first and fourth common regions and between said second and third common regions; a pair of output terminals; means coupling said third winding of said second core to said pair of output terminals; said unidirectional flux generated by said second winding of said second core interacting with said alternating flux generated by said first winding on said second core to develop a voltage in said third winding of said second core, the magnitude of said developed voltage being dependent on the magnitude of said unidirectional flux.

21. The system of claim 20 wherein said source of direct current includes rectifying means coupled across said output terminals; said means for coupling said source of direct current to said second winding of the first core includes a first potentiometer connected across said rectifying means; and said means for supplying direct current to said second winding of said second core includes a second potentiometer connected across said rectifying means.

22. A frequency quadrupling system comprising: an input circuit; an output circuit; a source of AC voltage; means coupling said source to said input circuit; a magnetic core; a first Winding wound on said core; means coupling said first winding to said input circuit whereby an alternating current is passed through said first winding and an alternating magnetic flux is generated in said core, said alternating flux following first and second paths in said core; a second winding wound on said core; a source of direct current; means coupling said source of direct current to said second winding, direct current passing through said second winding generating a unidirectional magnetic flux in said core, said unidirectional flux following third and fourth paths in said core; said first path sharing a first common region in said core with said third path and a second common region in said core with said fourth path, said second path sharing a third common region in said core with said third path and a fourth common region in said core with said third path and a fourth common region in said core with said fourth path, said fluxes being in opposing relationship in two of said common regions whereby the reluctance of said common regions is reduced, and in additive relationship in the other two of said common regions whereby the reluctance of said other two common regions is increased, each of said first, second, third and fourth paths including one opposing flux common region and one additive flux common region; a third winding wound on said core, said third winding being inductively coupled to said second Winding and being responsive to the interaction of said fluxes for producing an output voltage; and means coupling said third winding to said output circuit, the magnitude of said produced voltage being controlled by the magnitude of said unidirectional flux; a second magnetic core; a first winding wound on said second core; means coupling said first winding of said second core to said output circuit whereby an alternating current is passed through said first winding of said second core and an alternating magnetic flux is generated in said second core, said alternating magnetic flux following first and second paths in said core; a second winding wound on said second core; means for supplying direct current to said second winding of said second core, direct current passing through said second winding of said second core generating a unidirectional magnetic flux in said second core, said unidirectional flux following third and fourth paths in said second core; said first path sharing a first common region in said second core with said third path and a second common region in said second core with said fourth path, said second path sharing a third common region in said second core with said third path and a fourth common region in said second core with said fourth path, said fluxes being in opposing relationship in two of said common regions whereby the reluctance of said common regions is reduced, and in additive relationship in the other two of said common regions whereby the reluctance of said other two common regions is increased, each of said first, second, third and fourth paths including on opposing flux common region and one additive flux common region; a third winding wound on said second core, saidthird winding being inductively coupled to said second winding of said second core and being responsive to the interaction of said fluxes for producing an output voltage; the magnitude of said produced voltage being controlled by the magnitude of said unidirectional flux.

23. The system of claim 22 wherein said source of direct current includes rectifying means coupled across said output terminals; said means for coupling said source of direct current to said second winding of the first core includes a first potentiometer connected across said rectifying means; and said means for supplying direct current to said second winding of said second core includes a second potentiometer connected across said rectifying means.

24. An AC power regulating power supply comprising: a transformer having a high reluctance ferromagnetic core, primary and secondary windings on said transformer to provide transverse magnetic fields in said core, and an intermediate winding to provide a magnetic field parallel to that created by said secondary winding; a feedback circuit coupled to said secondary winding for developing a DC signal representing the level of AC power derived from said secondary; means for applying said DC feedback signal to said intermediate winding to control the AC power transfer from said primary to said secondary winding inversely with changes in said feedback signal; and means to bias the fields in said core so that the AC power transfer through said transformer is performed as a linear function of said feedback signal, no saturation occurring in said transformer during normal operation. 7

25. The AC power regulating power supply defined in claim 24 wherein a rectifier is employed to develop a DC output signal from said secondary winding, said feedback circuit including a transistor for receiving a sample of the DC output signal, said transistor serving as an inverting amplifier to reduce the amount of DC bias applied to said intermediate winding for increases in the DC level of said output signal and to increase the amount of DC bias applied to said intermediate Winding for decreases in the DC level of said output signal, whereby AC stabilization is accomplished in a DC power supply.

26. A system for controlling the coupling between an input circuit and an output circuit, comprising: a source of AC voltage; means coupling said source to said input circuit; said output circuit including rectifying means and means coupled to said rectifying means for sensing the output voltage; a ferromagnetic core having four common regions and first and second portions joining said four common regions; a first winding wound on said core with its axis extending between said first and second common regions and between said third and fourth common regions; means coupling said first winding to said input circuit whereby an alternating current is passed through said first winding and an alternating magnetic flux is generated in said core; a second winding wound on'said core with its axis extending between said first and fourth common regions and between said second and third common regions; a source of direct current, said source of direct current including said sensing means whereby said direct current is responsive to said output voltage; means coupling said source of direct current to said second winding, direct current passing through said second winding generating a unidirectional magnetic flux in said core; a third winding wound on said core with its axis extending between said first and fourth common regions and between said second and third common regions; means coupling said third winding to said output circuit; said unidirectional flux generated by said second winding interacting with said alternating fiux generated by said first winding to develop a voltage in said third winding, the magnitude of said developed voltage being controlled by the magnitude of said unidirectional flux.

27. The system of claim 26 wherein said source of direct current includes a first transistor having its collectoremitter path connected across the output of said rectifying means, a resistor connected across said output of said rectifying means and means connecting the base of said transistor to said resistor and wherein said means coupling said direct current source to said second winding includes a conductor connected to the collector of said transistor.

References Cited UNITED STATES PATENTS 2,623,205 12/1952 McCreary 32356 X 2,843,215 7/1958 Streuber 32356 X 3,134,964 5/1964 Wanlass 340174 3,354,384 11/1967 Benjamin 32125 X JOHN F. COUCH, Primary Examiner.

A. D. PELLINEN, Assistant Examiner.

US. Cl. X.R. 

